U.S. patent number 4,149,755 [Application Number 05/801,865] was granted by the patent office on 1979-04-17 for fluidizable material handling apparatus.
Invention is credited to Charles S. Alack, Avrom R. Handleman.
United States Patent |
4,149,755 |
Handleman , et al. |
April 17, 1979 |
Fluidizable material handling apparatus
Abstract
An improved material handling apparatus or container for
transporting, storing, and unloading a load of powder, granular,
particulate or other fluidizable material. The container has a
pallet base which includes a discharge opening and an inclined load
supporting deck with the discharge opening located at the lowermost
portion of the deck at one side of the pallet whereby substantially
all the fluidizable material in the container may be readily
unloaded. The container includes a porous cloth diaphragm held in
place overlying the deck by means of a retainer spline inserted
into a groove in the pallet along with the diaphragm in such manner
that the spline self-locks in the groove upon tension loading being
applied to the diaphragm thus preventing the diaphragm from pulling
free of the pallet during fluidization of the load. A vent valve is
provided for maintaining pressure within the container during
fluidization of the load within a predetermined pressure range to
maintain shape and structure while the container is being unloaded
without limiting the flow of fluidizing air but preventing
excessive pressure from being applied to the bag. Another
embodiment of the container of this invention is disclosed which
lessens the danger of explosion or fire due to the discharge of
static electricity while handling potentially dangerous materials
or while operating in dangerous environments.
Inventors: |
Handleman; Avrom R. (St. Louis,
MO), Alack; Charles S. (St. Louis, MO) |
Family
ID: |
25182216 |
Appl.
No.: |
05/801,865 |
Filed: |
May 31, 1977 |
Current U.S.
Class: |
406/90;
137/527.8; 206/597; 383/105; 406/146 |
Current CPC
Class: |
B65D
88/72 (20130101); Y10T 137/7903 (20150401) |
Current International
Class: |
B65D
88/00 (20060101); B65D 88/72 (20060101); B65G
053/66 () |
Field of
Search: |
;302/53,54,35
;222/195,462 ;251/338 ;137/527.8 ;220/203,206 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Nase; Jeffrey V.
Attorney, Agent or Firm: Koenig, Senniger, Powers and
Leavitt
Claims
What is claimed is:
1. A container for containing a load of granular, particulate,
powdered or other fluidizable material and for fluidizing the load
for unloading it from the container, said container comprising:
a pallet base having a plurality of legs engageable with the ground
for supporting the container and the load, said legs being spaced
for accommodating the tines of a forklift vehicle to facilitate
forklift transport of the container and said load, an upwardly
facing deck on said pallet base for supporting said load, said deck
sloping downwardly toward one side of the pallet base, a porous
diaphragm overlying said deck and defining a plenum between said
diaphragm and said deck, an inlet adapted for the introduction of
air under pressure into said plenum for fluidizing the load bearing
on said porous diaphragm, and a bag of synthetic resin film, coated
fabric, or other limp sheet air impervious material secured to said
pallet base and extending up above said deck for containing said
load of particulate or powder material, an outlet in communication
with said bag for the discharge of the load of material, the upper
end of the bag constituting a mouth of the bag for delivery of said
load into said bag; and
means for releasably securing the lower end of the bag to the
pallet base in sealed relation thereto so as to prevent air
pressure developed within the bag during the fluidization of said
load from pulling the bag off the pallet base so long as the air
pressure does not exceed a predetermined range;
means sealingly connected to said bag at the mouth of the bag for
venting air from within said bag during fluidization of said load,
said means for venting air comprising a valve, said valve including
a body through which the fluidization air flows and a valve member
movably mounted within said body, said member moving in response to
the pressure of the fluidization air acting thereon through a
succession of positions between a fully open position and a flow
blocking closed position, said valve member having means biasing it
toward the closed position, said biasing means operating to reduce
the closing bias on the valve member as the valve member moves
through the succession of positions from the flow blocking closed
position to the fully open position, said valve member and body
together defining a variable cross-section flow area that provides
a variable resistance to the flow of the fluidization air so that
air pressure upstream of the valve in the bag is maintained within
a predetermined range, the air pressure in the bag being sufficient
to hold the bag erect yet not so great as to pull the bag from the
pallet base during fluidization of the load.
2. A container as set forth in claim 1 wherein said valve member is
a damper and wherein said biasing means is adjustable to control
the magnitude of the closing means.
3. A container for transporting and storing a load of powder,
particulate, or other fluidizable material and for the fluidized
unloading of the load therefrom, said container comprising a pallet
base adapted for forklift transport of the container, a bag of limp
sheet material secured to the pallet base for containing said load,
means defining the bottom of said bag for fluidizing said load upon
the passage of compressed air therethrough,
means releasably securing the lower end of the bag to the pallet
base in sealed relation thereto so as to prevent air pressure
developed within the bag during the fluidization of said load from
pulling the bag off the pallet base so long as the air pressure
does not exceed a predetermined range;
an outlet in communication with said bag for the discharge of
fluidized material therefrom, and means connected to said bag for
venting the air from within said bag during fluidization of said
load, said means for venting air comprising a valve, said valve
including a body through which the fluidization air flows and a
valve member movably mounted within said body, said member moving
in response to the pressure of the fluidization air acting thereon
through a succession of positions between a fully open position and
a flow blocking closed position, said valve member having means
biasing it toward the closed position, said biasing means operating
to reduce the closing bias on the valve member as the valve member
moves through the succession of positions from the flow blocking
closed position to the fully open position, said valve member and
body together defining a variable cross-section flow area that
provides a variable resistance to the flow of the fluidization air
so that air pressure upstream of the valve in the bag is maintained
within the predetermined range, the air pressure in the bag being
sufficient to hold the bag erect yet not so great as to pull the
bag from the pallet base during fluidization of the load.
4. A container as set forth in claim 3 wherein, said biasing means
is adjustable to regulate the air pressure within said bag to be
within said predetermined pressure range.
5. A container as set forth in claim 3 wherein said valve member is
a damper and wherein said biasing means is adjustable to control
the magnitude of the closing bias.
Description
BACKGROUND OF THE INVENTION
This invention relates to material handling apparatus and more
particularly to a pallet molded of synthetic resin material or the
like adapted to form part of a container for transporting,
supporting, and storing a load of fine granular, particulate,
powdered or other fluidizable material, and for fluidized unloading
of the load from the container.
The pallet of this invention represents an improvement over the
container disclosed in the coassigned U.S. Pat. No. 4,007,694, and
commercially available from the assignee of this invention,
Semi-Bulk Systems, Inc. of St. Louis, Mo. under their registered
trademark AIR PALLET. The pallet disclosed in the above-noted
patent is generally circular, as viewed from above, having a number
of legs spaced for the entrance of the tines of a forklift from any
of four directions. The pallet has a peripheral wall extending
around the pallet and an upwardly facing deck supported by the
peripheral wall for supporting the load. The deck slopes downwardly
toward one side of the pallet and is adapted to have a porous
diaphragm of cloth or the like secured thereto with the diaphragm
covering the deck. An outlet opening is provided in the peripheral
wall of this prior art pallet above the level of the deck at the
lowest side thereof through which the powdered load may be
discharged or unloaded. An inlet opening also extends through the
peripheral wall for introducing compressed air into the space
between the diaphragm and the deck. The compressed air flows
upwardly through the porous diaphragm for fluidizing the powdered
load bearing against the diaphragm.
The diaphragm of this prior art container was secured to the pallet
by a spline held in place within a groove by means of staples
driven into the pallet. The spline merely distributed the loading
of the diaphragm to the staples. However, upon fluidizing the load
in this prior pallet, the air pressure beneath the diaphragm would,
on occasion, apply tension loading on the staples and pull them
free of the pallet thereby releasing the diaphragm and preventing
fluidization of the remaining portion of the load. When the
diaphragm pulled loose, refurbishment of the pallet was required
prior to reuse.
In many uses of the container of this invention, such as where the
empty containers must be air transported or where the containers
are used to contain toxic materials, it is desirable that
essentially all of the material be emptied from the container
during unloading thereby to minimize spilling of the material
during handling of the empty containers.
The prior art container described in the above-mentioned patent had
a tubular plastic film bag secured to its pallet. This bag was
generally of the same diameter as the pallet (e.g., about 42 inches
in diameter) and was of sufficient height to contain a desired
quantity of powder (e.g., 500-4,000 pounds or more). The bag was
typically attached to the peripheral wall of the pallet by means of
a metal strap band on the outside of the bottom of the bag,
tightened therearound and secured in place. Typically, this
strapping band was of the well known type (nylon) used to band
shipping containers commercially available from Signode Corporation
of Chicago, Ill. and other companies. Upon pressurizing the
interior of the bag during fluidized unloading of the load, the air
pressure would, on occasion, pull the bag from between the strap
and the pallet with the resultant loss of fluidization air and
spillage of the powdered load. Although this rarely occurred, it
was a serious problem when it did occur because the escaping powder
often prevented resealing of the bag to the pallet and thus the
load could not be fluidized for unloading and would continue
spilling from the container. It was also recognized that because
the pallet was preferably molded of synthetic resin material, it
suffered from some degree of inherent dimensional instability and
it would relax when a strap was tightly applied therearound.
It was also found that the pressure buildup within the container
would reduce fluidizing air volume to merely equal the volume of
powder and air discharge from the container thus limiting the
degree of fluidization and the discharge of material from the
container.
Due to the flow of material into the container during filling and
due to the flow of air through the fluidized material and the flow
of the fluidized material from the container during unloading, it
has been found that a static electricity charge could build up on
the container and pose a danger when handling potentially explosive
or flammable materials or when unloading relatively safe materials
in a hazardous environment (e.g., in a hydro carbon
environment).
Still further, the discharge conduit on prior art containers would,
on occasion, pull loose from the pallet during unloading or would
not properly seal relative to the pallet with consequent leakage of
the material during unloading.
SUMMARY OF THE INVENTION
Among the several objects and features of the present invention may
be noted the provision of a material handling container or pallet
adapted to support a load of granular, particulate, powder, or
other fluidizable material and adapted to fluidize the load for
efficient and rapid discharge of substantially all the load from
the container leaving little residue therewithin; the provision of
such a pallet having a porous diaphragm secured thereto in such
manner that the diaphragm may be readily installed and yet can
resist being pulled from the pallet by air pressure during
fluidization of the load; the provision of such a pallet which
substantially uniformly fluidizes the load therewithin; the
provision of such a pallet which may have a plastic film or other
flexible bag readily secured thereto for containing the load, the
bag being secured to the pallet in such manner that the bag resists
being pulled from the pallet during fluidization of the load and
that the bag is effectively sealed relative to the pallet to
prevent leakage of the load; the provision of such a pallet in
which the bag may be readily secured to the pallet without damage
to the bag or the pallet and with a minimum amount of labor
required; the provision of such a pallet in which the air pressure
within the container during fluidized unloading is maintained
within a predetermined pressure range for maintaining the structure
and shape of the fluidized contents in the otherwise flexible
container without restricting air flow and for minimizing the
possibility that the bag may be pulled from the pallet; the
provision of such a pallet of a container which is safe in handling
materials which may explode or ignite when exposed to open static
electricity sparks; the provision of a probe for such a container
which may be readily and effectively sealed and secured relative to
the discharge opening of the container; and the provision of such a
container which is of rugged and economical construction, and which
may be repeatedly reused with a minimum amount of
refurbishment.
Briefly, a material handling container or pallet of this invention
for supporting a load of granular, particulate or powdered material
and for pneumatically fluidized unloading of the load from the
pallet includes pallet base having a plurality of legs engageable
with the ground for supporting the pallet and the load carried
thereby, the legs being spaced for accommodating the tines of a
forklift vehicle to facilitate forklift transport of the pallet and
the load. The pallet further includes an upwardly facing deck for
supporting the load, the deck sloping downwardly toward one side of
the pallet, and a peripheral wall extending around the pallet
joining the upper deck and the legs. A porous diaphragm overlies
the deck and defines a plenum between the diaphragm and the deck.
An inlet is provided in the pallet for the introduction of air
under pressure into the plenum for fluidizing the load bearing on
the porous diaphragm. An outlet is provided which extends through
the peripheral wall of the pallet for providing communication
between the space above the porous diaphragm and the exterior of
the pallet, the inner end of the outlet being disposed at the
above-mentioned one side of the pallet adjacent the lowermost
portion of the deck being generally flush with the deck, and
angling downwardly from its inner end below the level of the deck
whereby the fluidized load flows down the inclined deck toward the
inner end of the outlet and thence down the outlet.
In another embodiment of the material handling container or pallet
of this invention, generally similar to that described above, means
is provided for securing the diaphragm to the pallet. This securing
means comprises an upwardly facing groove in the deck of the pallet
under the outer margin of the diaphragm, and an elongate spline or
retainer of relatively stiff material having a plurality of teeth
on one side thereof. The spline is insertable into the groove along
with the diaphragm so that the teeth engage the diaphragm and bear
against one side wall of the groove, and with the other side of the
spline bearing against the other side of the wall of the groove
whereby upon introduction of compressed air into the penum for
fluidizing the load with resultant pressurization of the diaphragm
and application of tension loading to the diaphragm, the spline
self-locks in the groove and securely holds the diaphragm in place
on the deck.
In still another embodiment of the container of this invention
generally similar to the containers above described, means is
provided for sealably securing the bag to the pallet and for
preventing air pressure from within the bag present during
fluidization of the load from pulling the bag from the pallet. The
pallet has a continuous, outwardly projecting flange around its
peripheral wall and the bag has its lower end folded on itself to
form a hem and a cord is disposed within the hem, the hem fitting
over the outside of the flange. The means securing the bag to the
pallet comprises a hoop clamp which fits over the flange on the
outside of the hem. The clamp includes means for circumferentially
tightening the clamp on the hem and on the pallet for sealingly
clamping the bag to the pallet whereby upon pressurization of the
bag during fluidization of the load and upon the bag being pulled
upwardly by the air pressure therewithin, the cord engages the
clamp and prevents the bag from slipping relative to the clamp and
to the pallet.
In still another variation of a container of this invention, means
is provided for venting the container (as defined by the bag) and
for maintaining an air pressure within the storage space within a
predetermined pressure range during fluidization of the load.
In still another embodiment of this invention similar to those
described above, the bag is specified to be made of an electrically
conductive material and means is provided for electrically
grounding the bag thereby to minimize the buildup of static
electric charges on the bag.
Further in accordance with this invention, a probe is provided
which is adapted to be removably inserted into the outlet opening
of the pallet and sealed relative thereto. The probe includes a
tubular body, an outwardly protruding shoulder extending
circumferentially around the body, a ring slidable axially on the
body toward and away from the shoulder, deformable seal means
disposed around the body between the shoulder and ring, and lever
means manually movable between a release position in which the seal
means is substantially free of compression and a seal position in
which the seal means is compressed between the ring and the
shoulder for effecting outward expansion of the seal means so as to
sealingly engage the walls of the pallet discharge opening.
Other objects and features of this invention will be in part
apparent and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a material handling container
or pallet of this invention for fluidized unloading of fluidizable
material;
FIG. 2 is an enlarged plan view of the pallet base of the container
of this invention illustrating a discharge outlet for the fluidized
load, an air inlet, an air distribution network in the upwardly
facing deck of the pallet, and a porous diaphragm overlying the
deck;
FIG. 3 is an enlarged cross-sectional view taken along line 3--3 of
FIG. 2 showing the discharge outlet of the container;
FIG. 4 is an enlarged cross-sectional view taken along line 4--4 of
FIG. 2 illustrating means in accordance with this invention for
securing the diaphragm to the pallet and means for securing the bag
to the pallet;
FIG. 5 is an enlarged side elevational view with parts broken of a
valve of this invention for venting the container and for
maintaining the pressure of the fluidizing air within the container
within a predetermined pressure range during fluidization of the
load;
FIG. 6 is an enlarged view of a probe of this invention for being
releasably and sealingly secured within the discharge opening of
the pallet, the probe being shown in its sealed position;
FIG. 7 is an enlarged side elevational view of the clamp of this
invention for clamping the bag to the pallet;
FIG. 8 is a view taken along line 8--8 of FIG. 4 illustrating a
spline for securing the diaphragm in place on the pallet; and
FIG. 9 is a view similar to FIG. 4 illustrating a modification of
the container of this invention incorporating an electrically
conductive liner within the bag;
Corresponding reference characters indicate corresponding parts
throughout the several views of the drawings.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, a container of this invention for
transporting, storing, and unloading a load of powder, granular,
particulate or other fluidized material is indicated in its
entirety at reference character 1 and is shown to include a
one-piece pallet base 3, preferably molded of a suitable synthetic
resin material (e.g., polyethylene or nylon), and a tubular bag 5
or other enclosure secured to the pallet for defining a storage
space therewithin in which a load of fluidizable material is
contained. The pallet includes a plurality of legs 7 (for example,
12 legs) engageable with the ground for supporting the container
and the load therewithin, the legs being spaced to receive the
lifting tines (not shown) of a forklift so that the loaded
containers may be readily moved about. The bag may be of any
suitable material, such as a limp coated fabric, or other air
impervious limp sheet material, but it is preferably of a tough,
strong plastic film as will be hereinafter specified. As indicated
in FIG. 1, circumferential straps 9 may be optionally installed
around the bag during or after filling to provide additional
circumferential support for the bag. The quantity of material
constituting a load may vary greatly depending on the material and
container size. In many instances, the container of this invention
is used primarily to transport and store so-called "semi-bulk"
quantities of material (i.e., more than a bag full but less than a
truck or railroad car full of fluidizable material).
As is best shown in FIGS. 1 and 3, pallet 3 includes an outer,
generally vertical peripheral wall 11 defining the outside of the
pallet. An outwardly projecting, continuous flange 13 extends
around the pallet at the top of wall 11 for purposes as will
appear. The pallet further includes a generally planar load
supporting deck 15 inclined downwardly toward one side of the
pallet relative to the lower ends of legs 7. As is shown in the
drawings, pallet 3 is preferably a hollow, unitary molded plastic
structure and is preferably fabricated by well known rotational
molding techniques. It will be understood, however, that the number
in which pallet 3 is fabricated and specific details of its
structure may be varied significantly and still be within the scope
of this invention. As disclosed in the above-discussed co-assigned
U.S. Pat. No. 4,007,694, the load supporting deck 15 of the present
invention is preferably spaced from supports formed within the
pallet and is flexible or deformable under the weight of the load
supported thereby so as to deflect downwardly thereby to rest on
supports so that the weight of the load is transferred to legs 7
and so that the deck need not resist the entire weight of the load
supported thereby.
Pallet 3 of this invention further has an outlet opening, generally
indicated at 19, at the side of the pallet adjacent the lowermost
edge of inclined deck 15 extending from the space above the deck
through peripheral wall 11 for the discharge of material within the
container. This discharge opening is defined by conduit walls 21
through the peripheral wall. The outlet is adjacent the lowermost
portion of deck 15 and is generally flush with the deck and angles
downwardly from its inner end below the level of the deck toward
the inlet end of the outlet and thence down and out of the
container via the outlet. The pallet further includes a second
opening constituting an inlet 23 for the introduction of compressed
air or other gas for fluidizing the load in a manner that will
appear.
Pallet 3 further includes a porous diaphragm 25 overlying deck 15
with a space between the diaphragm and the deck constituting a
plenum chamber 27. Compressed air or other gas introduced via inlet
23 enters the plenum and passes through the porous diaphragm so as
to fluidize the load of fluidizable material within bag 5 bearing
on the diaphragm. In accordance with this invention, deck 15
includes a plurality of upwardly facing open grooves or channels
constituting an air distribution network, as generally indicated at
29, for substantially uniformly distributing air pressure within
plenum 27 beneath diaphragm 25 to facilitate uniform fluidization
of the load over the entire working area of the diaphragm. This air
distribution network includes a main air channel 31 in
communication with air inlet 23. The main air channel extends
around the outer margin of deck 15 and, as shown in FIG. 2, the
outer margin of diaphragm 25 overlies the main air channel and an
outer circumferential retainer groove 33. The air distribution
network still further includes a plurality of secondary air
channels 35 radiating from a common point of locus P and
intersecting the main air channel 31 at substantially equal
intervals therealong. The air distribution network includes a
plurality of tertiary air channels 37, these tertiary air channels
being shown to be curvilinear and to intersect the secondary air
channels 35. The common point P is located adjacent outlet opening
19 and the secondary air channels 35 radiate therefrom. The common
point P is also shown to be the common center of the curvilinear
tertiary air channels 37. Main air channel 31 is of a depth
substantially greater than the secondary air channels and the other
air channels are so sized relative to one another as to facilitate
equal distribution of air pressure from one channel to another,
especially upon initial introduction of compressed air into plenum
27 when the diaphragm is pushed down under the weight of the load
against deck 15.
In accordance with this invention, improved means is provided for
rapidly and securely fastening diaphragm 25 to the pallet in such
manner as to prevent the diaphragm from becoming dislodged or
partially dislodged from pallet 3 during fluidization of the load
due to air pressure beneath the diaphragm from pulling it from the
pallet. As previously mentioned, the outer margins of the diaphragm
overlie retainer groove 33 which extends continuously around the
outer perimeter of deck 15 and which outlines opening 19 (see FIG.
2). An elongate retainer spline 39 of a relatively stiff material
(e.g., stainless steel or the like) having a series of serrated
teeth 41 on one side thereof is inserted down into groove 33 along
with diaphragm 25, with one side (i.e., teeth 41) bearing against
one side face (i.e., the inner side face toward the center of deck
15) of groove 33 and with the other side of the spline bearing
against the other side face of the groove. As best shown in FIG. 4,
spline 39 is crimped along its entire length so that it has a
generally flattened V-shaped configuration when viewed in
cross-section. The spline includes base portion 42 on one side of
the crimp, and teeth 41 project outwardly from the other side of
the crimp (see FIG. 8). Teeth 41 are generally triangular when
viewed in plan and may, for example, have a length of about 0.25
inches (0.63 cm.). Spline 39 may, for example, have about 5 teeth
per inch (2 teeth per cm.). The spline further includes tabs 43
extending outwardly from the outer edge of base portion 42. These
tabs may, for example, be spaced on one inch (2.5 cm.) centers and
be about 3/32 inches (0.24 cm.) long. Spline 39 is inserted into
groove 33 with teeth 41 pointing downwardly and toward the inner
generally vertical wall of the groove with base portion 42 being
parallel to and bearing against the outer generally vertical wall
of the groove. Thus, the tips of teeth 41 uniformly engage the
diaphragm and hold it firmly against the inner wall (bottom inner
corner) of the groove. Staples 44 are preferably driven into the
outer wall of groove 33 so as to engage selected tabs 43 for
holding the spline in place in the groove. Upon introduction of the
fluidized air into plenum 27, the air pressure acting against the
diaphragm will tend to pull the diaphragm upwardly out of the
groove. However, as the diaphragm begins to move upwardly out of
the groove, teeth 41 which protrude at least partially through the
diaphragm, move along with the diaphragm and thus more fully
penetrate the diaphragm (if they have not already done so) and
further are caused to dig into the plastic material constituting
the inner wall of the groove. The outer edge of base portion 42 and
staples 44 engaging tabs 43 constitute a fulcrum about which the
spline rotates. The rotation of the spline about this fulcrum is
indicated by the arrows in FIg. 4. In this manner, the spline
self-locks in the groove and the application of additional tension
loading to the diaphragm tends to cause the teeth to grip even more
securely and thus effectively resists tension loading of the
diaphragm. It will be appreciated that staples 44 are primarily for
acting as a fixed fulcrum or pivot for the upper edge of the base
portion as well as for holding the spline in the groove prior to
the application of fluidizing air pressure to the diaphragm and
that the staples are substantially free of tension loading which
might tend to pull them from the pallet while the diaphragm resists
the pressure force. The staples are primarily subjected to shear
loading which does not tend to pull them from the pallet.
It has been found that a spline having the approximate dimensions
as indicated above effectively and efficiently fastens a variety of
types of diaphragms from relatively heavy canvas to a fine ripstop
nylon or parachute nylon. It has also been found that the spline
arrangement described above is effective in securing multiple plies
of cloth constituting the diaphragm and it has been still further
found that the teeth do not cut or penetrate through the diaphragm
to such a degree as to degrade its strength. This method of
attachment causes the diaphragm to form an air seal at the inside
of groove 33 so that the small holes made in the diaphragm by the
spline teeth are outside this air seal and do not leak any
substantial quantity of fluidizing air. As shown in the drawings,
spline 39 is substantially continuous along the length of groove
33, but it will be understood that a series of shorter lengths of
the spline could be placed intermittently around the diaphragm in
the groove. It will be noted that a diametric groove 33' is
provided in deck 15 for receiving a spline 39 so as to secure the
center of diaphragm 25 to the deck thereby to reduce the total
force on the peripheral spline.
As previously mentioned, container 1 includes bag 5 which is
removably and sealably secured to pallet 3. Bag 5, as heretofore
described, is an elongate tubular sleeve of a tough, strong plastic
film or the like. Specifically, in certain applications, plastic
coated fabric film such as is commercially available from the Van
Leer Plastics, Inc. of Houston, Texas under their trademark
VALERON, may be used. It will be understood, however, that a
variety of different films and bag configurations may be used in
conjunction with the container of this invention depending on the
quantity of product to be contained in the bag, the characteristics
(i.e., density, toxicity, etc.) of the product, the number of
desired reuses of the container, and other parameters.
In accordance with this invention, a split hoop clamp, as is
generally indicated at 45, is provided for releasably and sealably
fastening bag 5 to pallet 3 so as to substantially eliminate the
tendency of the bag to be pulled free of the pallet during
fluidization of the load due to air pressure within the bag, and to
substantially eliminate leakage of the product between the bag and
the pallet. As shown in FIG. 4, pallet 3 is formed to have the
above-mentioned continuous flange 13 extending circumferentially
therearound. By way of example, flange 13 has a heighth of
approximately 3/4 inches (1.9 cm.) and extends radially outwardly
from peripheral wall 11 approximately 1/4inch (0.63 cm.). In
accordance with this invention, the bottom margin of tubular bag 5
is folded back on its outside face so as to form a hem 47 (see FIG.
4). A cord 49, such as a stretchable elastomeric ring, a fiber
rope, or the like, is placed inside the hem below flange 13. It
will be noted that the double ply of the hem extends up above
flange 13. Clamp 45 is shown to comprise a hoop 51 of an
electrically conductive metal, such as mild steel or the like,
which is generally channel-shaped in cross section (see FIG. 4)
having a web 53 adapted to be generally parallel to and to be
cooperable with the outer face of flange 13 thereby to clamp bag 5
relative to the pallet. The clamp further has upper and lower
flanges 55a, 55b. The outer edges of these flanges are preferably
bent back on themselves so as to protect the bag from being cut or
otherwise damaged by the strap. It will be understood, the lower
margin of a bag 5 containing an unfluidized load of fluidizable
material has a tendency to droop down over the outside of clamp 51.
In accordance with this invention, flange 55a of hoop clamp 51
positively holds the bag on flange 13 of the pallet and positively
prevents the weight of the fluidizable material in the bag from
pushing or pulling the bag and hoop clamp 51 off the pallet.
Still further in accordance with this invention, the outer face of
flange 13 may optionally have a layer of compressible foam material
56 adhered thereto. This foam material is shown to be about as wide
as flange 13 and to have a thickness of about 1/8 inch (0.31 cm.).
The foam layer is disposed between the double plies of hem 47 and
flange 13 so as to constitute a compressible surface against which
the bag hem may be compressed and sealed. This foam takes up
dimensional variances in the pallet and in the clamp and enables a
leak-tight seal to be made within a relatively wide band of
dimensional tolerances.
Hoop clamp 51 further includes a tension connector, as generally
indicated at 57, for adjustably drawing the ends of the clamp
together and for securely clamping bag 5 on pallet 3. As shown in
FIG. 7 tension connector 57 comprises a pair of upper and lower
tubular barrels 59a, 59b, respectively, secured to each end of the
split hoop clamp for receiving upper and lower bolts 61a, 61b. By
tightening the bolts, the hoop may be tightened a desired amount
within the limits of bolts 61a, 61b. By selectively tightening
either the upper or lower bolts somewhat more than the other, the
upper and lower edges of the clamp may be adjusted independently of
one another so as to vary the degree to which the upper and lower
portion of the clamp grips the bag. The hoop further includes a
resilient tongue 63 of relatively thin gauge stainless steel or the
like which is secured to one end of the hoop clamp and which
extends beneath the other end of the hoop clamp to protect the bag
from damage (i.e., from being torn) as the hoop is tightened. While
tension connector 57 has been herein described as a bolt tightening
arrangement, other types of tensioning devices, such as overcenter
buckles and the like, may be used.
In accordance with the above-described bag securing means of this
invention, as fluidizing air enters bag 5 from plenum 27 through
diaphragm 25 and as air pressure within the bag builds up so as to
exert vertical tension force on the bag (thereby maintaining its
shape in a semi-rigid manner) which would tend to pull it away from
deck 15, any slippage of the bag relative to the hoop clamp is
prevented by cord 49 after the cord comes into contact with the
bottom flange 55b of the hoop clamp. Thus, the securing arrangement
for the bag of this invention can be said to be self-locking and to
thus positively prevent the bag from being pulled off the pallet
during fluidized unloading.
After filling bag 3 with product, the upper margin or mouth of the
bag is twisted or otherwise drawn shut so as to at least partially
close off the mouth of the bag. As has been heretofore
conventional, a length of plastic tubing 65 or the like
constituting a vent for the bag is inserted in the constricted
mouth of the bag and the bag is clamped, as by means of a wire tie
67 or the like so as to releasably close and seal the mouth of the
bag with respect to the vent tube (see FIG. 1). Vent conduit 65,
discharge outlet 19, and compressed air inlet 23 may be capped by
suitable plastic caps or plugs (not shown) inserted therein so as
to seal the load within container 1. Thus, upon unloading the
container, the plugs are removed from the discharge outlet, the
fluidizing air inlet and from the bag vent tube.
As the fluidizing air enters the bag from plenum through porous
diaphragm 25, it is vented from the bag via vent tube 65 after it
has flowed through the product within the bag. As heretofore
mentioned, the degree of fluidization of the product or material
within bag 5 may vary, depending on the quantity of product in the
bag, as the product is unloaded. Also, the pressure within the bag
may occasionally decrease or increase as the product is
intermittently discharged from the bag. In certain instances, an
increase in air pressure within the bag will pull the bag free of
the pallet. In other instances, a decrease in pressure within the
bag below a specified level will cause an erect bag to lose
rigidity and to permit the load to shift so as to cause the
container to tip.
In accordance with this invention, a vent valve, as generally
indicated at 69, is connected to a vent valve conduit 71 which is
sealably connected to vent tube 65 for venting the fluidizing air
from within bag 5. Thus, vent valve 69 constitutes means for
venting the fluidizing air from the bag and for maintaining air
pressure within the bag within a predetermined range during
fluidization of the load so as to hold the bag erect and to prevent
pressure within the bag from pulling it from the pallet during
fluidization of the bag. Vent valve 69 comprises a body 73 having
an inlet 75 connected to vent conduit 71 and an outlet 77 with a
damper or flapper valve member 79 pivotally mounted offcenter
between the inlet and outlet. A counterbalancing crank arm 81
rotates with the flapper valve member and carries a
counterbalancing weight 83 for biasing the flapper valve member
toward its closed position in which it substantially blocks the
flow of fluidizing air from the bag. Since valve member 79 is
pivotally mounted offcenter, air pressure from within the bag tends
to cause the flapper valve member to pivot or rotate relative to
body 73 from its closed position toward its opening position
against the bias of counterbalancing weight 83. The counterweight
83 being positioned to reduce its closing bias on the valve member
79 as the valve member 79 moves through a succession of positions
from the flow blocking closed position to the fully open position.
Thus, by adjusting the position of counterbalancing weight 83 along
the length of crank arm 81, vent valve 69 can be selectively
adjusted to maintain air pressure within the bag within a selected
pressure range so as to insure proper fluidization of the load
within the bag, to prevent the build up of excessive air pressure
within the bag, and to maintain a sufficient pressure within the
bag to hold the bag erect thus preventing the load from shifting as
the load is discharged therefrom. This pressure range may, for
example, vary between 2 and 40 inches (5 and 100 cm.) of water. It
will be understood that means other than weight 83, such as a
spring, may be used to counterbalance valve member 79 against
opening under the influence of fluidizing air pressure within the
bag.
As previously mentioned, fluidized product from within bag 5 is
discharged from the container via outlet 19. As was conventional in
prior art containers, such as disclosed in the above-mentioned
coassigned U.S. Pat. No. 4,007,694, the discharge conduit or hose
was removably inserted into the discharge opening of the pallet so
that the product discharged therefrom could be conveyed to a remote
location, such as to a hopper, an eductor, or the like. Heretofore,
the discharge conduit of these prior art containers had a probe
which was forcibly inserted into the pallet discharge opening so as
to be frictionally sealed and held in place on the pallet. However,
due to dimensional variances of the pallet discharge opening, due
to inadvertant bumping of the discharge conduit, and due to air
pressure within the discharge opening, the prior art probes would,
on occasion, become dislodged from the pallet with consequent
spillage of the product and termination of unloading from the
container.
In accordance with this invention, a probe, as generally indicated
at 85, is provided for insertion into and for being positively and
sealingly connected to outlet opening 19 of pallet 3 of this
invention so as to receive the material being discharged from the
pallet. A conduit or hose 87 is secured to probe 85 for conveying
the discharged material from the pallet. The probe has a tubular
body 89 of circular cross section and has an outwardly extending
flange 91 adjacent the outlet end of the body with the surface of
the flange facing away from the end of the body constituting a
shoulder 93. As shown in FIG. 6, shoulder 93 is preferably undercut
for purposes as will appear. An expandible seal 95 of hard rubber,
plastic or the like is positioned on the body behind shoulder 93. A
compression ring 96 is located on body 89 behind the seal and is
axially movable on the body between a retracted position (not
shown) in which it is substantially clear of seal 95 and in which
the seal is substantially free of compression and a position (as
shown in FIG. 6) in which the ring compresses the seal between
itself and shoulder 93 thereby to cause the seal to expand radially
outwardly into firm gripping and sealing engagement with walls 21
defining outlet 19 of pallet 3. It will be understood that the seal
fits into the undercut of shoulder 93 to hold the seal as it is
compressed thereagainst. As shown in FIG. 6, the seal extends past
the inner surface of peripheral wall 11 so that upon being
compressed, it engages the walls of the outlet and bulges out on
the inside of the peripheral wall to a diameter larger than the
outlet thereby to positively prevent the probe from being withdrawn
from the opening. With the seal frictionally engaging walls 21 of
outlet 19, the probe firmly engages the pallet and thus prevents
inadvertent removal of the probe from the pallet and the probe is
effectively sealed relative to the pallet so as to prevent leakage
of product from the outlet 19 during unloading. The probe further
includes a handle 97 joining two cam levers 99a, 99b on opposite
sides of body 89, the cam levers being pivotally secured to the
body as indicated at 100. Each of the cam levers has a respective
rotary cam 101a or 101b adjacent its pivotal connection. These cams
cammingly engage the rear face of compression ring 96 opposite seal
95 and cause the ring to move axially along the body member toward
shoulder 93 so as to move the ring toward its compression position.
Handle 97 and cam levers 99a, 99b constitute manually operable
means for compressing and releasing seal 95.
Probe 85 may optionally include an air tube 103 for directing air
into the fluidizable material as it flows into outlet 19 from
within bag 5 thereby to insure that the material will continue to
flow through the outlet and will not bridge or jam in the outlet.
This discharge air tube is shown to comprise a tubular member
extending endwise from the top of the probe from the inside of body
89. The tubular member extends into the probe body and has external
connections 105 thereon so that an air line (not shown) from a
compressed air source may be connected thereto. Thus, in operation
compressed air may be directed through air tube 103 and discharged
into the powder within outlet 19 thereby to breakup and to keep the
powdered material flowing through the outlet. Compressed air for
air tube 103 may optionally be applied by a bypass from the
fluidizing air line adapted to be inserted in inlet 23.
As heretofore mentioned, in handling certain products which pose a
risk of explosion or fire, or in handling relatively safe materials
in a hazardous environment (such as in a hydrocarbon environment in
a chemical plant or the like) it is necessary that the container 1
of this invention be properly grounded so as to lessen the danger
of the discharge of static electricity which could cause an
explosion or fire. In accordance with this invention, bag 5 may be
made electrically conductive either by placing an electrically
conductive liner 107 inside bag 3 or by providing an electrically
conductive coating 109 on the inside surface of the bag. For
example, liner 107 may be of an electrically conductive plastic
film such as is commercially available from the 3M Company of
Minneapolis, Minn. under their registered trademark VELOSTAT. As
shown in FIG. 9, liner 107 is placed inside bag 5 so as to form a
multi-ply bag and the liner and the bag are folded up to form hem
47'. Clamp 45 contacts liner 107 to make good electrical contact
therewith. The plastic film constituting bag 5 may be made
electrically conductive by electrodepositing a layer of aluminum or
other electrically conductive metal on one face (the inside face)
of bag 5 so as to constitute coating 109 (see FIG. 4). Such coating
of plastic film is commercially available from the above-noted
supplier of bag 5.
In forming hem 47 at the bottom margin of the bag, the electrically
conductive inner face 109 of the bag faces outwardly when folded to
form the hem and thus the electrically conductive metallic hoop
clamp makes good electrical contact with the conductive surface of
the bag around its entire bottom portion. Regardless of whether an
electrically conductive bag or a liner 107 is used, a grounding
wire 111 (as shown in FIG. 1) is clipped onto clamp 45 thereby to
electrically ground the bag during filling, unloading, and other
operations so as to dissipate static electric charges on the
bag.
Still further in accordance with this invention, it is sometimes
necessary to electrically ground vent conduit 71 and discharge
conduit 87 so as to further prevent the discharge of static
electricity. These conduits may be made of electrically conductive
hose material, such as is commercially available from the 3M
Company under their registered trademark VELOSTAT. Of course, these
electrically conductive conduits may be properly grounded by
connecting grounding wires (not shown) to the conduits. Thus, the
entire container 1 of this invention may be effectively and readily
grounded.
In handling potentially explosive or flammable materials, it may be
desirable to fluidize the material during unloading with a gas
other than air. For example, an inert or chemically inactive gas,
such as nitrogen or the like, may be used in place of compressed
air thereby to even further diminish any likelihood of fire or
explosion during unloading.
It will be understood that an outlet for the discharge or vacuum
withdrawal of fluidizable material within container 3 may be
provided by inserting a tube (not shown) into bag 5 from the top
and sucking on this tube. Of course, this withdrawal tube is sealed
relative to the bag and the bag is vented to the atmosphere.
In view of the above, it will be seen that the several objects of
the invention are achieved and other advantageous results
attained.
As various changes could be made in the above constructions without
departing from the scope of the invention, it is intended that all
matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *